Curved RF electrode for improved Cmax

Abstract

The present invention generally relates to a MEMS device and a method of manufacture thereof. The RF electrode, and hence, the dielectric layer thereover, has a curved upper surface that substantially matches the contact area of the bottom surface of the movable plate. As such, the movable plate is able to have good contact with the dielectric layer and thus, good capacitance is achieved.

The invention claimed is: 
     
       1. A method of manufacturing a MEMS DVC, comprising:
 forming one or more electrodes over a substrate; 
 depositing a dielectric layer over the electrodes and the substrate; 
 chemical mechanically polishing the dielectric layer to expose the one or more electrodes, wherein the chemical mechanical polishing results in a convex upper surface of the one or more electrodes; and 
 forming a plate electrode over the one or more electrodes, wherein the plate electrode has a bottom surface having a concave portion overlying the convex upper surface of the one or more electrodes. 
 
     
     
       2. The method of  claim 1 , further comprising:
 depositing a second dielectric layer over the chemical mechanically polished dielectric layer and the one or more electrodes. 
 
     
     
       3. The method of  claim 2 , wherein the second dielectric layer is conformally deposited. 
     
     
       4. The method of  claim 3 , wherein the second dielectric layer has a convex surface overlying the convex upper surface of the one or more electrodes. 
     
     
       5. The method of  claim 4 , further comprising:
 depositing a sacrificial layer over the second dielectric layer, wherein the sacrificial layer has a convex surface overlying the convex upper surface of the one or more electrodes. 
 
     
     
       6. The method of  claim 5 , wherein forming the plate electrode comprises forming the plate electrode over the sacrificial layer. 
     
     
       7. The method of  claim 6 , wherein the concave portion is in contact with the convex surface of the sacrificial layer. 
     
     
       8. The method of  claim 7 , further comprising removing the sacrificial layer. 
     
     
       9. The method of  claim 1 , wherein the one or more electrodes includes an RF electrode. 
     
     
       10. The method of  claim 9 , wherein the RF electrode has the convex upper surface. 
     
     
       11. The method of  claim 10 , wherein the dielectric layer is deposited by PECVD. 
     
     
       12. The method of  claim 11 , wherein the dielectric layer is selected from the group consisting of silicon oxide, silicon oxynitride, silicon nitride, silicon dioxide and combinations thereof.